In open spinal vertebrae surgical procedures, the surgeon makes an incision through the skin and muscle tissue and exposes the area to be worked on using retractors separating the tissue above the adjacent vertebral bodies and the interposed disc. Using cutting devices such as a spoon curette or rongeur, the surgeon cuts away the bone and disc material and prepares a space for a spinal fusion device to be placed.
In minimal invasive surgery, the large incision is not used and in its place a smaller cut is made just large enough to position a small hollow tube or cylinder into the disc space between the two vertebrae to be fused together. It is through this tube that the cutting tools must pass to remove the disc material and prepare the space for a fusion implant device. The vast majority of these cutting devices operate by rotational cutting of the tissue to be removed. This allows for a circular cross sectional removal of the disc, but requires rather difficult angulation to flatten or widen the space being prepared. A secondary issue is to flex into a tube fitting compressed size; the blades typically have two or more separate cutting blades as in U.S. Pat. No. 5,709,697. This enables the blades to deflect into a tube, but uses a small pointy tip prone to break when in use leaving metal fragments.
Very importantly, these rotational devices are limited in vertical reach that can be achieved. In some small patients, this represents little trouble, but in larger boned patients, the vertical space required for the implant can exceed the capacity of the device.
The present invention as described hereinafter avoids these issues in a new and improved way to provide the surgeon a much simpler and efficient way to prepare the disc space for implantation.